1. Field of the Invention
The present invention relates to a foam sensor of a drum washing machine, which can sense if a foam electrode terminal is electrically short-circuited, and freely select an installation location of a thermistor and of the foam electrode terminal, and a drum washing machine having the same.
2. Description of the Related Art
Generally, a washing machine is an apparatus for removing contaminants stained on clothes, bedclothes or the like (hereinafter, referred to as “laundry”) by the action of detergent-dissolved water or clean water (hereinafter, referred to as a “washing water”).
FIG. 1 is a front cross sectional view schematically illustrating the interior of a drum washing machine according to the related art. Referring to FIG. 1, the drum washing machine according to the related art includes a cabinet 2, a tub 4 mounted in the cabinet 2 for containing washing water therein, a drum 6 rotatably disposed in the tub 4 for accommodating linen, and a motor (not shown) for rotating the drum 6.
To the tub 4, a water supply device 8 for supplying the washing water from the outside into the tub 4 and a drainage device 10 for draining the washing water in the tub 4 to the outside are connected.
The drainage device 10 includes a drainage hose 11 connected to a lower portion of the tub and a drainage pump connected to the drainage hose 11.
The washing machine further includes a pressure sensor 14 installed for sensing the level of the washing water supplied into the tub 4, a pressure chamber 16 formed at a lateral side of the drainage hose 11, and a water pressure transmitting portion 18 connecting between the pressure sensor 14 and the pressure chamber 16 so as to transmit the pressure of the washing water to the pressure sensor 14.
A method for sensing foam of the thus-constructed drum washing machine according to the related art will now be described below.
When a power is applied to the drum washing machine, washing water flows into the tub 4 through the water supply device 8. When the washing water fills up the tub 4, a pressure is formed in the pressure chamber 16, and the pressure in the pressure chamber 16 changes according to the level of the washing water.
Hence, the pressure sensor 14 senses a pressure change in the pressure chamber 16 through the pressure transmitting portion 18, and accordingly a control unit (not shown) determines a washing water level.
If excessive foam is generated in the tub due to an excessive use of detergent or the like at the time of washing, the pressure in the tub 4 rises to more than a predetermined value.
That is, since the pressure in the tub 4 increases as the pressure of the washing water and the pressure of the foam are added, it is determined if excessive foam is generated according to a change in the value sensed by the pressure sensor 14. Thus, once it is determined that excessive foam is generated, a foam removal operation in which water supply and drainage are repeated is performed.
However, the drum washing machine according to the related art is constructed so as to sense if excessive foam is generated only when the pressure in the tub 4 rises to more than a predetermined value. Accordingly, foam can be sensed only after foam fills up the tub 4. Therefore, the foam reduction operation is lengthened, which takes a lot of washing time and cost, and which cannot prevent the risk of fire caused by corrosion of peripheral parts, electrical leakage, etc.
In recent times, a foam sensor formed of an electrode terminal for sensing foam is used. However, in a case where a connecting line of the foam sensor is cut off or a poor connection occurs or the like, it is determined that no foam is generated, thereby failing to prevent the generation of excessive foam.